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MG Midget and Sprite Technical - Engine cut out

On the way home Friday night, the engine just cut out and wouldn’t restart. Usual checks and nothing found. Given my previous woes I immediately thought I had done something incorrect with the Carb. Took it off, all good, and confirmed fuel getting to carb all ok.
So I looked at the electrics side. All cables connected good. I recently added a new loom and all wiring is good.
So this leaves the distributor and coil, I think, With the ignition on and points open I get 12v to sw and cb side of the coil, so not the coil. This leaves condenser and the points themselves.
I get 12v when testing at point 1 and nothing when testing at point 2, the base plate.
The Haynes manual version I have seems to have error in the testing sequence. It repeats testing the same thing and gives a different fault diagnosis, so I’m slightly lost.
I can just change the points and condenser, but I wouldn’t mind knowing is this is the issue. Anyone have any pointers? Especially as the car just stopped working on the way home. If it is just the points etc I will likely move to an electronic ignition from a reliability point of view.



BruceBurrowes

Change one at time and see what happens as you seem to have covered most of the likely suspects?
You may want to consider changing the rotor arm for a red one from the Distributor Doctor.
Jeremy MkIII

As you have insulation between the points, point 1 should be 12v and point 2 should be 0v. As its the base plate, which is connected to the engine, it will always be 0v. If you take the insulation out and the points are closed, point 1 would become 0v.
If, under this condition, you use a piece of a none conductor to flick open the points you should get a spark as the points open. If so this means the LT side is OK.
Now, disconnect the HT lead connecting the coil to the distributor, from the distributor. Put the free end close to the engine. A gap of less than 1/4 inch will be OK. Try to wedge it there if you don't want to risk getting a shock. Now flick open the points again and you should see a fat spark jump from the HT lead to the engine. If so your HT is OK. If not suspect your coil.
If your HT is ok then it must be your dist cap or rotor arm.
It's most unusual just to stop. I suspect your coil especially if it is new or fairly new. Modern coils, along with other modern ignition components, are very poorly made and unreliable.
Rob
MG Moneypit

I have only been stranded once by the midget in 49 years. I was gunning down an entrance ramp and when I reached traffic speed, the engine quit.

After having it trailered home and following several hours of changing this and adjusting that, it turned out to be... the rotor. It had a crack down the side and this got dirty enough to provide a decent short to earth.
Glenn Mallory

Be very careful about replacing points and particularly condenser with modern made examples as they can be very poor quality and unreliable, to be sure get them from Dissy Doc. - http://www.distributordoctor.com/
Nigel Atkins

To check the rotor arm. Take the lead from the coil to the dizzy can and disconnect it at cap. Place cap aside. Hold lead just off brass contact on dizzy rotor. Flick the ignition. If you get a spark the rotor is u/s as it is allowing a spark through to earth. No spark is good.
Alan Anstead




Dry joints and a lack of spark can affect many of us, of a certain age, over the winter months but can also affect our Sprites and Midgets at any time of the year. I have broadcast this information before but the problems still arise and may not be known by newer members.
Firms such as Aldon Automotive and Distributor Doctor are able to provide better quality alternatives to the commonly available reproduction rotor arms which routinely fail and leave people stranded.
Electronic ignition can be fitted concealed in the distributor and replacing the contact breaker and unreliable modern condensers but the rotor arm, depending upon which sort of electronic ignition is used will still remain. My own choice has been the Aldon / pertronix ‘Hall effect’ system that has proven reliable over fifteen years and many miles at home and abroad.
Some rotor arms manufactured in recent years have been failing because the typical ‘mix’ used in the injection moulding process now contains more carbon blacking than of old and is more conductive to electricity. It has been found that the rivet which holds the brass contact inlay into the moulding, on reproduction rotors, is slightly longer than the original bringing it too close to the spring clip on the underside. The High Tension (HT) current, averaging 30,000 volts, is always looking for the easiest route to earth and shorts out, from the tip of the over length rivet, through the reduced thickness of the more conductive plastic and the spring clip on the underside of the rotor arm to earth out down the distributor shaft. This results in no spark at the sparking plug and a ‘failure to proceed’ from your Sprite or Midget. The system sometimes rectifies itself on cooling but then repeats itself with increasing frequency until the rotor permanently short circuits.
Distributor Doctor offers ‘Lucas red rotor arms’ which are modelled on the original 1960s design but made from modern materials on the latest machinery to very close tolerances and have achieved a good reputation for reliability. The integrally moulded brass inlay dispenses with the troublesome rivet. The increased insulation properties of the body makes them suitable for use with high voltage ignition coils and electronic ignition kits. The spring clip on the underside, in conjunction with a revised internal tolerance assures a really snug fit upon the distributor spindle even on old and slightly reduced diameter mountings.
Even with the uprated rotor arms it is worth being vigilant and occasionally checking the security of the brass contact.
When fitting a rotor arm consider applying some petroleum jelly to the distributor drive shaft rotor arm seating to eliminate moisture as I have been called upon to work on a car where the distributor drive seat rusted such that it grew so much in size that it cracked the rotor arm that had to be chiselled off. I also tend to use petroleum jelly on most electrical joints to stop them being effected by damp and corrosion.
Part number for Sprite / Midget 25D distributors is DRB101
Part number for alternative 45D type distributors is DRB104
Distributor Doctor can be found at www.distributordoctor.com and Aldon Automotive at www.aldonauto.co.uk.
Electronic ignition systems are easily fitted to Sprite and Midgets and are available for both Positive and Negative earth configurations fitting inside a vehicle’s distributor with no outward sign of conversion. It is easy to carry a spare distributor base plate set up with points and condenser in case of the rare, but not unknown, instance of the electronic system failing at the roadside. Why not also consider carrying a spare coil? I have used a Lucas DLB105 “gold’ coil on both of my Sprites for years, for they are relatively cheaply purchased at the car shows and can be affixed to a suitable bolt in the engine compartment, there being no need to clutter the boot, and be easily accessible if they are ever needed.
Alan Anstead.
Alan Anstead

All excellent advice Alan, and written in a non-patronising way, recognising individual preferences but still supplying the explanations and information needed. Looks very much like the text of one of your MASCot contributions!
GuyW

My write up for Mascot. I use it a lot when members phone with problems. I usually send it to participants when organising tours. It had been used a lot as the word has not got around and folks are still suffering the same old problems.
Alan
Alan Anstead

ALWAYS check for continuity between the base plate and the distributor body first.

The earthing of the base plate is done by that very fragile wire which terminates under the phillips head screw in the body.

Without an earth to the base plate, nothing works!
Chris at Octarine Services

The clue could be that it conked out at running temperature but tested OK when cold. This to me points to a hot running coil that's breaking down, a broken earth wire in the base plate or a failing rotor arm. I always suspect dry crimped joints if that's what you have, under the blue sleeve - a proper soldered joint will always be far more reliable.
f pollock

A good crimp is often better than a solder. The blue connector and wires connection doesn't look pretty but 'looks' as if it'd be solid - but it might not be, certainly always worth checking.

New wiring loom but what about all the connections on it?

At the risk of stating the bleedin' obvious, points gap checked and for opening and closing.

Nigel Atkins

Many thanks for the test routines, very helpful. Anyone know a of definitive list, that contains all of these?

Rob you highlighted doing the test with the points closed, I did this and got a reading of 0.4v. I havent completed the flick open tests. I thought my testing had ruled out the coil, but I'll look at these.

Alan thanks for the article.

Chris/F Pollock regards the conking out at running temp, it subsequentely wouldnt restart. So of the three items, the broken earth wire seems the most plausible. Just to confirm, is the wire you are meaning the blue one in my picture?

The comment about the base plate earthing correctly may be an issue as when I removed the points there appeared to be some white "material" behind it, which has been wiped off now.

The only thing I can think this could be was from the wing being resprayed as its the same colour, but this seams highly unlikley to me as it's nowhere else.

Thanks for pointing me to the distributor doctor, very helpful. New points, condensor, rotor arm and coil on the way.

I will try and do some more testing before I fit the new parts, but many thanks.
BruceBurrowes

Bruce, What's the red bit in your dizzy photo?
GuyW

No - the earth wire is the grubby black cloth covered wire close to the baseplate.

If you got a reading of 0.4v at 2 with points closed then the earthing is at fault - it should be zero.
Chris at Octarine Services

Flimsy earth wire. -



Nigel Atkins

Guy,
red bit is something (plastic?) used as insulation.
Nigel Atkins

Bruce,
again, if you need a new earth wire get it from the Dissy Doc.

On installing your new parts consult the Driver's Handbook for correct order of fitting the insulation bush (as you have now) and for gap setting and dissy lubrication.

Illustration and cover from my copy, such a useful book.






Nigel Atkins

So just to give an update, I contacted Dr Dizzy and have now put in new points, rotor arm, condensor and a new coil. All fitted and working fine. I completely forgot about the earth wire, but will do some testing.

I don't think the coil was the issue but I can feel the difference at the lights.:)

Ive also just changed the sparkplugs from 6 to 7's and this again seems to have made a difference. When my engine is switched off it "runs" a bit more. It was suggested to me this is because the engine is hot enough to be still running, so higher number sparkplugs might solve this. I also bought some 8's and may change them on the day at Anglesey to see if I can notice a difference.

Nigel many thanks for highlighting the Driver Handbook. I had mainly used Haynes but the Handobook has a lot of useful technical information, seems daft I never looked there.

Car is running ok, but not great, and its beyond my knowledege to improve at the moment. It's booked in to be tuned up next Friday with a local chap who makes and sells superchargers for a series. I have no intention of fitting a supercharger's (yet), he just has a lot of a series experience.

If anyone is at Angelsey, see you there
BruceBurrowes

I would stick to the 6s - if the engine runs on when switched off, get into the habit of flooring the accelerator as you switch off, it will kill any run on.
Chris at Octarine Services

Bruce,
generally its workshop manuals for repairs but Driver’s Handbook for prevention.

Obviously the DH refers to circumstances, and when, the cars were new back in the 60s and 70s and some things have progressed (a lot) since then (some have not), and the cars are used (and abused) since then too.

Unless there are changes to your engine generally NGK BP6E(S) are the accepted plugs (or Champion if you want to be traditional).

As you're running on traditional CB points (shudder! from me) you do need to check them at some point after installing them and at service intervals, even good quality ones can wear and need adjustment as the rest of the dissy can be ancient/worn/lack of proper service/abused.

Often taking it to an expert will discover a chink missing or missed from the basics and once they sort that they can progress as much as is possible at the time.

Don't worry about actual numbers on gauges or graphs just feel for overall improvements in actual use and road performance (power, mpg).
Nigel Atkins

Run-on can indeed be caused by a hot running car. Cause can be a weak mix as well as any obvious cooling issues. Clean out carb(s) properly - jets especially. Then set it/them correctly. Mix, balance, idle. Check air filter also. This may also explain any rough running.

Timing may be out. Strobe is the way to go to set dynamic, but follow the manual for the easier static timing and you won't be far out. I used a test lamp.

Joining wires - solder every time. It's a pain, but there is nothing better. Do it properly.




Oggers

>>Joining wires - solder every time. It's a pain, but there is nothing better. Do it properly.<<

I disagree - not always - crimping is widely recognised as better in many circumstances.

Nigel Atkins

Nigel

Widely recognised by whom? By folk who take short cuts? By folk who cannot solder? If joining or splicing wires there is nothing to beat solder Terminal connections are a different matter, but personally I still prefer solder even here.
Oggers

I agree with Nigel on the crimping. I used to work for a connector company and we had some of our connectors on programs like Voyager, Viking, Apollo, the Lunar Rover, the Space Shuttle and numerous military aircraft and all were crimp contacts. The Voyager probes are still working after 40 + years of flight in a rather hostile environment.
Martin

Hi

Re connecting wires: as a non-expert I've generally been replacing like with like when replacing wire connections e.g. replacing bullets with soldered bullets or spade connectors with crimped spade connectors etc.

It took me a while to realise that the crimp needs to be really tight which I cant do by hand so ive had to resort to a few taps woth a small cross pein hammer. Then they are REALLY firm. I also like the fact that the back part crimps the insulation so the wire doesn't flex so much. I used to favour soldered joints but again as a non-expert I made the occasional dry joint which had to be resoldered from scratch. Sometimes I found it difficult to clean off grease or oxidation and if you use an acid flux if you dont clean it off properly it stays slowly eating through the unsoldered part of the wire. Also the soldered section is completely inflexible so the unsoldered part of the wire flexes more.

So I'm leaning towards using crimps even when replacing solder or bullets. And there are experts on here whose advice I generally follow!

My two cents worth.

Brendon
(Perhaps I should offer my crimping services to SpaceX)

B M Le Page

Disagree entirely. Whilst crimps are fine in themselves, they simply cannot compete with a decent soldering job. Crimping only makes surface electrical contact on the outside strands thereby increasing resistance, and in extremis, reducing the capability to allow current to flow - as effectively you are reducing the cross sectional area of the the wire. Crimping also imparts a huge stress on the individual wire strands - often breaking them if they are copper alloy - and the crimp itself is usually some horrible cheap metal, which whilst conductive is nowhere near as conductive as solder.

Solder on the otherhand has none of these flaws. It creates a homogenous and low resistance connection with all strands, and imparts strength to the splice.


Oggers

Well that's put me in my place! I think the point I was trying to make is that its possible for someone like me to make a poor soldered joint that can cause problems down the line. .As you said - it to be 'decent'!

I wasn't really trying to tread on toes or express an opinion on the relative merits - just relating what I had found when using the two methods.

Oops!
B M Le Page

BM le P. I was certainly not putting anyone in their place, merely outlining my take on the merits of soldering over crimping. Soldering is quite a straightforward way to obtain a very solid, robust joint. There are a few basic points.

Use flux - helps the solder to flow
Heat the work not the solder
Lead solder is easiest to work with
Use a decent iron. 25W is fine for most things.
Once the solder flows, add the solder gradually. The solder changes colour when it gets up to melting point. Keep adding solder until it has permeated through all the strands. It's quite satisfying watching it ooze through them!
Keep the work stable when soldering.
Don't touch it for at least 10 secs. afer soldering
Recommend heat shrink

You won't regret it, and it will be very useful tool in your box to use elsewhere.
Oggers

Because I've read the pros and cons of both methods I invariably do both; a good crimp with a decent over-centre crimper, then run solder into the connector.
David Smith

David

I do that on terminal connections!

Oggers

Brendon,
I used to be able to make a reasonable crimped connection with the cheap crimp pliers but moved on to the ratchet crimpers because of problems with my hand and wished I'd done so decades back.

As I have small hands I could even do with smaller ratchet crimpers but I've not seen any.

If you don't want to buy a set see if you can borrow some for the connections, and automatic wire stripper, both make the work so much easier (with a little practice).

I did wonder what you'd used on the insulated blue connector in the dissy as it looked odd to me.

Photo one, an example of a ratchet crimping tool for insulated connectors (different tool for non-insulated).

Photo two, an example of an automatic wire stripper.






Nigel Atkins

Brendon,
for the bullets, wait for it . . .




I use a (ratchet) crimper! :)

An example of such is shown in photo one.

I also use a bullet closer tool, I prefer the cheaper version, to, er, close the bullets into the bullet connector evenly and with greater ease than other methods, and without implaling a digit with a small sharp screwdriver.

Photo two shows an example of a cheaper version of the bullet closing tool.






Nigel Atkins

David,
I remember, in the past, reading somewhere about a/the disadvantage of adding soldering to a crimped connection but can't remember the details. It might even have been in one of the Archives here, but I think it was elsewhere on t'web (not in a paper printed book IIRC).

But given the state of some PO wiring and the fact that things continue to work in spite of it I think any reasonably completed joint, be it solder, crimp or both combined, is going to be good.
Nigel Atkins

Hi Nigel

This is really helpful thanks.Yes I use a ratchet crimper but my hand and fingers have too many problems even so. Hence the final tap.

I'm not taking any responsibility for the blue connector on the distributor that's the finest workmanship of whoever made the electronic ignition!

I think its time I added the automatic wire stripper - again the cheap one is getting frustrating.

The bullet closing tool is tempting too. Seems a good plan - come up with a poor design and then sell you the tool to make it work.Just kidding.

I might just have to go round the car randomly cutting wires and joining them together for fun.

Btw I've a friend down the road who has just rewired his Dellow and used to work for Lucas and he's been helpful too.He usually brings a jar of smoke with him.

Ive been trying to keep the interactions light but I think I'm going to keep my head below the parapet for a bit!
B M Le Page

Hi Nigel


In case you are interested here is a link to my first restoration. I blundered in with no experience or skill. Forum archives, books and YouTube made it possible. I taught myself everything including welding, a bit of fabrication and spray painting. Welding is ugly but thorough. I was pretty proud of the result and the chap who mot'd it said it 'drives exceptionally well'. I had it checked out for safety by an mg specialist in Uckfield.


https://1drv.ms/f/s!Atxys4LLN_Q8nL52Ni8-bfcfddL4AQ

The current sprite is going to be driven with occasional garaging to make improvements. At some point it will get the nut and bolt treatment.
B M Le Page

Hi Brendon,
well done on your resto. You're way ahead of me in all your car skills (not too much of a compliment as everyone else here is also way ahead of me).

Don't worry about you or anyone here disagreeing, things can't get heavy on such an insignificant thing as discussing, debating or even arguing, about old cars.

I think the only thing Oggers and I could ever agree on is that we would probably disagree on everything - but he might disagree with that. :)

I'm usually against the flow here as I loathe doing anything on my car other than driving it and I'm not too much of a traditionalist wanting to keep things like CB points and using Old Mcdonald's oils. :)

I'm glad that blue connector isn't your work.

With the crimp connections I was really thinking of bullet and terminal connectors, I've nothing against joining or extending wires by soldering but think it'd be better, if possible, to replace the whole length of wire - and have crimp connections on both ends. :)

I find the ratchet crimper a bit heavy and unbalanced in use and at the start at least the handles are open too wide for my hands but the ratchet action should complete the joint successfully if the connector is placed in the jaws correctly. I'll put up a photo of the instructions on mine.

As you've probably already found some of the crimped connectors can be of poor quality so you do need to shop around for them.

Using the tools I've cut, stripped and crimped bullets and connections on short tails of wires in situ behind the dash, I'd have never been able to solder in the same way.

As I use these tools so infrequently I usually do a couple of practice joints before doing the work to make sure the tools (I include myself in this description) are all doing a good job and working correctly.

As I learnt from posting here a few years ago and experience, a 25w soldering iron is often too weak to use on the car as it sits outside, fine unusually when working inside but sometimes it' not practical to get the wire out of the car to the bench.

I think the Lucas smoke jokes are fine but not accurate if you consider the wiring, connections and Lucas items can be many decades old and still working in many case despite use and abuse from the car owners.

The thing with actually using the car is that you soon discover that some modern made parts are so poorly made but that's just how it is, IMO better to use the car than not.

Keep posting Brendon and starting new threads both to ask and answer (or joke, debate, discuss) you have knowledge and experience to offer.
Nigel Atkins

The issue with crimping and soldering at the same joint is that the end of the crimped / soldered connection then becomes a rigid point that can break under vibration. The simple fix for this issue is to use a short length of heat shrink to bridge between the crimpm and the wire insulation. This removes the point of stress and makes a neat finish of the connection.

BTW I always remove the coloured plastic sleeve from crimp connectors (If I cannot find crimps without them) and use a crimp tool that once had a ratchet (long ago) but two small jaws for a solid dimpled crimp. The cheap pressed metal ones are a waste of time, and the ones with jaws colour coded to the crimps don't make as good a job as my old broken tool.

I tend to crimp only unless it is an exposed joint or one that takes a lot of movement (Heater switch for example), when I solder as well. EVERY joint gets a heat shrunk sleeve.

And as Nigel said the bullet pliers save stabbed fingers / hands.
Dominic Clancy

Thanks for all this detailed information.

Sorry for the Lucas joke - to be fair I've said to anyone who visits that its bodged wiring, poor earthing or lack of maintenance and such that seems to cause trouble. On my restored MG with everything cleaned up, properly earthed and meticulously following the wiring diagram the electrics worked perfectly till I sold it so I agree completely.

The issue of flexing and metal fatigue next to a rigid solder joint is an aspect I consider because I've experienced it (as in my first post) and I always use heat shrink to help with that. I'm probably over cautious because as Dominic says most joints don't flex anyway.

I'm definitely going to take the point about removing the coloured plastic sleeves. I have always assumed the manufacturer knows best but maybe not. This seems to be a recurring theme. With the replacement body panels didnt fit I just assumed I was doing something wrong.

X2 on the soldering iron after struggling I now have a 45W with adjustable temps

Cheers for an interesting debate!
B M Le Page

Nothing wrong with a crimped only joint imv for terminals (bullet, spade, ring) providing they're properly made with the insulation being clamped. The wire strands are clamped together so tightly that the current flows through the entire cable. Soldered joints are used more typically for components on circuit boards or within accessories e.g. diode pack in alternator.
Bill Bretherton

Brendon,
joking is allowed (noticed or not).

With the solder to crimp it was stiffness and something else [ETA: as well as what Bill has just put] but it really doesn't really matter. Adding solder then shrink wrap even on the bench would push my working on : driving the car ratio too far the wrong way, certainly wouldn't worry about it whilst having my shoulders on the seat trying to focus as I fiddle around making a connection in the limited and crowded space behind the dash. As you'll find running repairs can be different to restoration work.

I've not had problems with the coloured sleeves on the connectors, though some do look cheap, short and flimsy. The problem I had was with a modern made female spade connector of unknown origin that after two years opened its folds enough to not properly connect to the male part.

I'd have thought, but don't know, that if you remove the sleeves the size of the jaw opening on the ratchet crimper would then be the wrong size, - which ties in with the scan of the instructions I previously promised.



Nigel Atkins

Wow. Amazing what detailed instructions and advice there is on such a seemingly simple thing as crimping a wire. I'm always interested in the detail because I'm self taught.

I'm certainly not going to weigh in on the relative merits of the methods because I use both anyway.But regarding soldering as Oggers said lead solder works better but after sanding many square meters of lead paint and desoldering lead pipework in the houses I renovated and having been with my father gayly using red lead undercoat when it was real lead I feel I have ingested quite enough lead already. It probably explains some things. Also I want to learn lead loading so that will probably finish me off.

I think most people lie the twisted wires next to each other while soldering a joint in a length of wire. However I've seen (and tried to make) a joint where you fan out the strands of each wire and then interleave them (like interleaving your fingers) before rolling them together and then applying the solder. It makes a beautiful symmetrical oviod joint which is extremely strong and where the conductivity is good because all the strands are actually touching each other and its very satisfying!
B M Le Page

Brendon,

As I mentioned above, I worked for a connector company for 14 years. One of the first things I got to do was a crimp study. This involved crimping 50 contacts at different settings varying in 1 mil increments and using different wire sizes and taking measurements of each and every crimp from four sides and then doing a pull test and recording the pullout results to find out which setting is optimal. I don't remember how many total contacts were involved but there were a lot. So, yes, this seemingly simple operation is quite complicated and a week later I was glad when I finished it but I did know a lot about the process.

I like your method of soldering wires together. Sounds like a good solid joint.
Martin

Very good job on the restoration, good to have it recorded for posterity too.
Alternative suggestion for bullet pliers is a pair of water pump pliers, they've saved my fingers a few times.


Jeremy MkIII

I bought some cheap £5 water pump pliers from Screwfix and slotted the jaws specially for this job. About 1/5th the cost of the flimsy purpose designed ones that are sold! And you can still use them as pliers.😄


GuyW

The best joint of two lengths of wire is made by stripping 1/2 inch of each, overlapping the wires and twisting 1/4 inch of one wire around the other and vice versa, then soldering - keeping the solder to the twisted wires.

This results in a mechanically and electrically strong joint with a diameter similar to the wire insulation, so when covered with heat shrink looks neat and professional.




Chris at Octarine Services

Guy If you can believe it I've had water pump pliers in the drawer for years. In my head it's a plumbing tool. I must get it into my head to think creatively and repurpose things.

So now I've got a pair of waterpump pliers slash bullet connector tool in my drawer.

Brilliant!
B M Le Page

You might have to cut the handles down to get them to fit in behind the dash with everything fitted around the dash.

A good idea normally though, especially as waterpump pliers are often used as a crude tool in place of a better or more appropriate tool.
Nigel Atkins

This thread was discussed between 19/07/2020 and 11/08/2020

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.